For centuries, external and internal cog wheels and spur gears have been used to interconnect shafts on aligned and parallel axes, while bevel gears have been used to transmit rotational forces between shafts having axes that intersect with each other at fixed angles extending over the full range from 90.degree. to 180.degree.. During this century, hypoid gears have been developed to accomplish the same purpose with shafts that not only intersect with each other over the full range of wide angles but whose axes are offset (i.e., non-intersecting). For such known internal and external spur gearing, shaft alignment is an absolute necessity; and known bevel and hypoid gear pairs are designed specifically for only one predetermined angle between the axes of the gears.
There are, however, some known special coupling and joint arrangements for compensating for small shaft misalignments where forces are being transmitted between aligned axes that must experience small angular changes during operation. For instance, it is known to use double-crowned spur gears in nylon sleeves for coupling shafts that may experience slight relative movements in parallel offset (e.g., 0.040"/1 mm) or slight angular misalignment (e.g., &lt;1.degree.). However, for each significant degree of angular change (e.g., &gt;1.degree.) between the axes, a completely new set of mating gears must be designed and manufactured to assure proper coupling and transmission of the rotational forces.
Of course, there are known non-gear means for transmitting rotary motion between shafts experiencing angular change. Perhaps the best known of such devices are the universal joints used to connect the drive shafts and wheel axles of automotive vehicles. Such universal joints are often constructed in the form of two small intersecting axles, each held by a respective yoke. However, the shafts connected by such yoke and axle joints do not turn at the same rate of rotation throughout each entire revolution. Therefore, constant-velocity ("CV") joints have been developed (e.g., Rzeppa and Birfield) in which the points of connection between the angled shafts are provided by rolling balls which, during each revolution of the driving and driven shafts, roll back and forth in individual tracks to maintain their respective centers at all times in a plane which bisects the instantaneous angle formed between the shafts.
Such universal and CV joints are quite complex and relatively difficult to lubricate, and the design and manufacture of such joint components is widely recognized as a very specialized and esoteric art of critical importance to the worldwide automotive industry. While this CV joint art is very well developed, the joints are expensive, comprising many parts that are difficult to manufacture; and such joints are limited in regard to the rotational speeds that they can transmit and in regard to the angles over which they can operate. Further, the rotational speeds that can be achieved by such joints are limited by the inertia of the rolling balls whose motion must reverse during each revolution.
Our invention has broad potential utility in any technology in which motion is transmitted between axes that intersect at variable angles during operation; and, as shown in specific embodiments disclosed below, our invention has particular applicability to, and provides remarkable improvements in, the CV joint art, providing the basis for remarkably simplifying and improving the design of CV joints.